The present invention relates generally to a method of resist developing on a integrated circuit wafer, more particularly a silicon or GaAs wafer.
When developing lithographic patterns (formed by a photo process, E-Beam or X-ray) on integrated circuit wafers such as silicon or GaAs, uniformity of feature size can vary due to developer nonuniformity or develop time fluctuations. Typical prior methods make use of spray head developers, which have thermal and distribution nonuniformities across each wafer; and variable chemical properties are overcome by end pointing for wafer to wafer uniformity.
Apparati for liquid chemically developing silicon wafers are well known in industry. Disclosed in U.S. Pat. Nos. 3,769,992; 3,953,265; 4,021,278; 4,197,000; and 4,466,389, these systems all employ some form of spray nozzle to distribute development solution across the wafer's face. The major disadvantage with these systems is the thermal and distributional nonuniformities they produce.
U.S. Pat. No. 4,136,940 to Lin entitled "Resist Development Control System" teaches the use of a detector apparatus to determine resist development completion. The detector provides an incident light beam which illuminates a portion of the surface to be developed. Photodetectors positioned to intercept the reflected beams provide outputs corresponding to the light energy in the reflected light. As the development process begins, the light energy in the reflected beams changes. By continuously monitoring this energy level, the developing process can be terminated when this level reaches a given value.
U.S. Pat. No. 4,429,983 to Cortellino et al entitled "Developing Apparatus for Exposed Photoresist Coated Wafers" teaches the use of a development tank utilizing a rotatable, vertically translatable, shaft mounted workpiece for developing a single wafer. The wafer is secured to the workpiece, lowered into the tank of solution, and then rotated and vertically agitated for a period of time, estimating satisfactory development completion. The patent shows use of input and output ducts to transport new and used developer solution through the apparatus, but no attempt is made to continually circulate fresh developer into the tank.
U.S. Pat. No. 4,544,446 to Cady entitled "VLSI Chemical Reactor" discloses a vacuum chuck apparatus for liquid chemically developing silicon wafers. This device permits continuous processing through a series of sequential steps which practically eliminates contamination of wafers during processing. The patent teaches use of a fluid guide having a plurality of spaced holes which allow the even application of developer solution to the wafer, and a means for removing all waste developer. This patent also teaches endpoint detection as a means for controlling fluid flow into the chuck.
U.S. Pat. No. 4,231,811 to Somekh teaches a method of developing semiconductor material using a masking member having opaque and transparent areas. U.S. Pat. No. 4,468,857 to Christian teaches a method of manufacturing an integrated circuit using a wafer wherein fine alignment is achieved outside the active chip area. U.S. Pat. No. 4,696,833 to Monnig, teaches a method of providing uniform coatings to wafers by chemical vapor deposition. U.S. Pat. No. 4,706,374 to Murakami teaches a method of fabricating a semiconductor having p-type and n-type regions by immersing the substrate into an electrochemical solution.